A variety of treatments exists for dilating or removing atherosclerotic plaque in blood vessels. The use of an angioplasty balloon catheter is common in the art as a minimally invasive treatment to enlarge a stenotic or diseased blood vessel. When applied to the vessels of the heart, this treatment is known as percutaneous transluminal coronary angioplasty, or PTCA. To provide radial support to the treated vessel in order to prolong the positive effects of PTCA, a stent may be implanted in conjunction with the procedure.
Thrombectomy is a minimally invasive technique for removal of an entire thrombosis or a sufficient portion of the thrombosis to enlarge the stenotic or diseased blood vessel and may be accomplished instead of a PTCA procedure. Atherectomy is another well known minimally invasive procedure that mechanically cuts or abrades a stenosis within the diseased portion of the vessel. Alternatively, ablation therapies use laser or RF signals to superheat or vaporize the thrombus within the vessel. Emboli loosened during such procedures may be removed from the patient through the catheter.
During each of these procedures, there is a risk that emboli dislodged by the procedure will migrate through the circulatory system and cause infarction or strokes. Thus, practitioners have approached prevention of escaped emboli through use of occlusion devices, filters, lysing and aspiration techniques. For example, it is known to remove the embolic material by suction through an aspiration lumen in the treatment catheter or by capturing emboli in a filter or occlusion device positioned distal of the treatment area.
Prior art temporary filters or occlusion devices are associated with either a catheter or guidewire and are positioned downstream of the area to be treated. One prior art filter arrangement includes a dilatation balloon and a filter mounted on the same catheter. The filter is located distal to the dilatation balloon and consists of a filter material secured to resilient ribs. A filter balloon is located between the catheter exterior and the ribs. Inflation of the filter balloon extends the ribs outward across the vessel to form a trap for fragments loosened by the dilatation balloon. When the filter balloon is deflated, the resilient ribs retract against the catheter to retain the fragments during withdrawal of the catheter.
Another prior art device provides an expandable occlusion member mounted on a slender, elongate wire. The occlusion member is passed distal to the intended treatment site and expanded to obstruct the flow of bodily fluids during the procedure. An interventional catheter is guided to the treatment site over the wire and the vessel narrowing is enlarged. Any emboli produced are trapped upstream of the occlusion balloon. Bodily fluid containing the particulate is aspirated from the vessel, either through a dedicated lumen in the treatment catheter, or via a separate aspiration catheter that has been exchanged for the treatment catheter. Last, the occlusion member is collapsed and removed from the patient. The occlusion member may be an inflatable balloon or a mechanically expandable structure covered by a non-porous membrane.
Another prior art device includes a filter mounted on the distal portion of a hollow guidewire or tube. A moveable core wire is used to open and close the filter. The filter is secured at the proximal end to the tube and at the distal end to the core wire. Pulling on the core wire while pushing on the tube draws the ends of the filter toward each other, causing the filter framework between the ends to expand outward into contact with the vessel wall. Filter mesh material is mounted to the filter framework. To collapse the filter, the procedure is reversed; pulling on the tube while pushing on the core wire to draw the filter ends apart.
Another prior art device has a filter made from a shape memory material. The device is deployed by moving the proximal end of the filter towards the distal end. The filter is collapsed and withdrawn by sliding a sheath over the filter and then removing the sheath and filter together.
Another prior art filter device discloses a compressible polymeric foam filter mounted on a shaft that is inserted over a guidewire. The filter is inserted collapsed within a housing which is removed to deploy the filter once in position. The filter is retracted by inserting a large bore catheter over the shaft and the filter, and then removing the shaft, filter and catheter together.
Another prior art filter arrangement has a filter comprised of a distal filter material secured to a proximal framework. This filter is deployed in an umbrella manner with a proximal member sliding along the shaft distally to open the filter and proximally to retract the filter. A large separate filter sheath can be slid onto the shaft and the filter can be withdrawn into the sheath for removal from the patient.
Other known prior art filters are secured to the distal end of a guidewire with a tubular shaft. Stoppers are placed on the guidewire proximal and distal of the filter, allowing the filter to move axially independently of the guidewire. Sheaths are used to deploy and compress the filter.
A problem associated with prior art filter guidewires is the requirement for a sheath to envelop and collapse the filter before and after the treatment is performed. Sheaths that encase the filter often require large bores, with attendant bulky handling. It is time-consuming and cumbersome to exchange the sheath for the treatment catheter and to reverse this exchange step at the end of the procedure.
Another problem associated with guidewire-based devices in the prior art is that the clinician must decide whether or not to start the procedure with a filter (or occluder) guidewire. If the diseased conduit is particularly tortuous, the additional capture mechanism at the distal end of the guidewire may inhibit or interfere with initial crossing of the treatment site. In this case, the procedure may require initial negotiation with a standard guidewire, then advancement there over by the treatment catheter, then exchanging of the standard guidewire for a wire-based distal capture device. Besides the additional time and steps required, there is the extra cost of the two kinds of guidewires involved.
Finally, inflating occluding balloons on small diameter guidewires, such as those used in PTCA, requires the complexities of an external inflation accessory and a miniature sealing mechanism to sustain the balloon in occlusion mode while an interventional catheter is loaded over the proximal end of the guidewire.
With the above in mind, it is an object of the present invention to provide a temporary device for capturing embolic material that does not require an enveloping sheath to collapse the capture element for insertion or withdrawal.
Another object of the present invention is to provide a temporary device for capturing embolic material, wherein the device may be deployed and/or closed with a mechanism that is simple compared to the hydro-pneumatic devices of the prior art.
Another object of the present invention is to provide a temporary device for capturing embolic material, wherein an adapted guidewire may be used as a standard guidewire, then, as desired, a capture element may be introduced over the guidewire and deployed into apposition with the vessel of the patient.